Question

Answer 1

1, thay x=2 vào A ta có:
\(A=2^2-5.2+8=4-10+8=2\)

2, thay x=1,y=-1 vào B ta có:

\(B=1^3.\left(-1\right)+3.1.\left(-1\right)-\left(-1\right)^3\\ =-1-3+1\\ =-3\)

\(2,\left(x-\dfrac{1}{2}\right)\left(x^2+5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{2}=0\\x^2+5=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x^2=-5\left(ktm\right)\end{matrix}\right.\)

Answer 2

A)2
B)-3